Distributed Torque Generation System and Method of Control

ABSTRACT

An apparatus for an electrically powered terrestrial vehicle applies electrical energy to front wheels and to rear wheels. A control system receives desired acceleration inputs and provides target torque requirements to a plurality of adaptive field-oriented motor control circuits. One or more three-phase alternating current synchronous motors receive voltage magnitude and voltage frequency to generate torque, which is applied through a reduction gear. The reduction gear may be coupled to one wheel or a pair of wheels. Forward acceleration is favored over deceleration by a chosen ratio between reduction gearing of the front axle versus reduction gearing of the rear axle.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a non-provisional of Ser. No. 61/950,229 filed 10Mar. 2014 “Adaptive Torque Budgeting and Electric Motor Control System”which is incorporated by reference in its entirety and receives thepriority date thereof. Other related applications are docketsR-PTNTR201411-15.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

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THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

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INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISK OR ASA TEXT FILE VIA THE OFFICE ELECTRONIC FILING SYSTEM (EFS-WEB)

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STATEMENT REGARDING PRIOR DISCLOSURES BY THE INVENTOR OR A JOINTINVENTOR

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BACKGROUND OF THE INVENTION

1. Technical Field

The field of the invention is within motor vehicles, and morespecifically the control over distribution of torque generation by aplurality of electric motors located throughout the vehicle structure.

2. Description of the Related Art

It is known that torque vectoring is provided to all wheel drivevehicles. Torque vectoring is a known technology employed in automobiledifferentials. A differential transfers engine torque to the wheels.Torque vectoring technology provides the differential with the abilityto vary the power to each wheel. This method of power transfer hasrecently become popular in all-wheel drive vehicles. Some newerfront-wheel drive vehicles also have a basic torque vectoringdifferential. As technology in the automotive industry improves, morevehicles are equipped with torque vectoring differentials.

Differentials are known to refer to a particular type of simpleplanetary gear train that has the property that the angular velocity ofits carrier is the average of the angular velocities of its sun andannular gears. This is accomplished by packaging the gear train so ithas a fixed carrier train ratio R=−1, which means the gearscorresponding to the sun and annular gears are the same size. This canbe done by engaging the planet gears of two identical and coaxialepicyclic gear trains to form a spur gear differential. Another approachis to use bevel gears for the sun and annular gears and a bevel gear asthe planet, which is known as a bevel gear differential.

The fundamental concept of torque vectoring depends on the principles ofa standard differential. A differential shares available torque betweenwheels. This torque sharing ability improves handling and traction.Torque vectoring differentials were originally used in racing. Thetechnology has slowly developed and is now being implemented in a smallvariety of production vehicles. The most common use of torque vectoringin automobiles today is in all-wheel drive vehicles.

The main goal of torque vectoring is to vary a share of torque betweenor among wheels coupled to a motor or engine. Differentials generallyconsist of only mechanical components. A torque vectoring differentialoften includes an electronic monitoring system in addition to standardmechanical components. This electronic aspect is only to direct themechanical differential when and how to share the torque.

Torque vectoring differentials on front or rear wheel drive vehicles areless complex than all-wheel drive differentials. The two wheeldifferential only shares torque between two wheels.

A front-wheel drive differential must take into account several factors.It must monitor rotational and steering angle of the wheels. As thesefactors vary during driving, different forces are exerted on the wheels.The differential monitor these forces, and adjusts torque accordingly.Many front-wheel drive differentials can increase or decrease torquetransmitted to a certain wheel by changing the ratio between the twowheels. This ability improves a vehicle's capability to maintaintraction in poor weather conditions. When one wheel begins to slip, thedifferential can reduce the torque to that wheel, effectively brakingthe wheel. The differential also increases torque to the opposite wheel,helping balance the power output and keep the vehicle stable. Arear-wheel drive torque vectoring differential works the same way as afront-wheel drive differential, but doesn't monitor the steering angle.

Most mechanical torque vectoring differentials are on all-wheel drivevehicles. A first torque vectoring differential varies torque betweenthe front and rear wheels. This means that under normal drivingconditions, the front wheels receive a set percentage of the enginetorque, and the rear wheels receive the rest. If needed, thedifferential can transfer more torque between the front and rear wheelsto improve vehicle performance.

For example, a vehicle might have a standard torque distribution of 90%to the front wheels and 10% to the rear. Under harsh conditions, thedifferential changes the distribution to 50/50. This new distributionspreads the torque more evenly between all four wheels. Having more eventorque distribution increases the vehicle's traction.

There are more advanced torque vectoring differentials as well. Thesedifferentials build on basic torque transfer between front and rearwheels. They add the capability to share torque between a pair of frontwheels or a pair of rear wheels.

The differential monitors each wheel independently, and distributesavailable torque to match current conditions. One known mechanism firsttransfers power between front and rear pairs and subsequently shares theamount of torque transmitted to each rear wheel by a second differentialin series. The front wheels, however, do not receive different amountsof torque. Another known torque vectoring system adds a third mechanicaldifferential to share torque provided to the front pair of wheels.

Another known system supports 4 electric motors coupled by gearboxes andaxles to individual wheels. Negative torque is produced electricallyrather than applying brakes as mechanical systems do.

As is known, Mercedes Benz has provided a purpose built electric vehiclewith four synchronous independent electric motors. The engines make atotal of 740 (750 PS) and 1,000 Nm (737.5 lb-ft), which is split equallyamong the four wheels in normal driving conditions. Because all fourmotors are electrically-powered independently of one another translatesinto potentially high speed wheel control.

The conventional Mercedes approach are still mechanically linking eachmotor to its wheel by a reduction gearbox and axle. A much moreeconomical Tesla utilizes a single 3 phase AC induction motor and has aconventional mechanical power train. A conventional mechanical powertrain provides three differentials and reduction gearboxes. Aconventional power train must have the same reduction ratio from engineto the front axis as well as to the rear axis to enable all wheel drive.

It is known that torque vectoring is particularly suited to electricvehicles. Lotus has been evaluating and developing new systems andapproaches. When a driver turns the steering wheel, they expect thevehicle to change direction (yaw). The vehicle does not, however,respond immediately because tires take time to build up lateral forces,and the actual vehicle response may not be exactly what is required, orexpected.

Particularly at high vehicle speed, after an initial delay period (afraction of a second) the vehicle yaw rate can overshoot and oscillatebefore settling on a steady value. At very high speeds, or if thevehicle's suspension is poorly tuned or the operator poorly skilled, theoscillations can increase and the vehicle can go out of control. Even atlower speeds, the oscillations can make the vehicle feel less stable andthe driver may need to make multiple steering adjustments tosuccessfully follow the intended path.

Conventional vehicle suspension is tuned through bump steer, staticsettings, etc, to minimize the oscillations and to give a stableresponse at all vehicle speeds and loading conditions, but any increasein stability is at the expense of vehicle agility and the vehicleresponse can become disappointing.

It is known that when a vehicle has independent control over the driveand braking torques to each wheel (for instance, electric hub motors),there is an opportunity to improve the vehicle yaw response.

One approach has been by increasing the drive torque to a pair of tandemwheels (e.g. port), and creating an effective braking torque at theopposite pair of tandem wheels (e.g. starboard). These drive torques arein addition (or subtracted from) to the normal drive torques required tocontrol vehicle speed. In other words, turning or yaw occurs when oneside of a car is traveling faster than the other side.

Maximum Yaw Turning Moment (Torque)

Independent of the steered angle of the wheels, a yaw moment isgenerated when the resultant vector of the tire forces is perpendicularto a line through the center of gravity. The resultant force is thevector sum of lateral force and driving/braking force. The maximum yawmoment (if required) is obtained when the resultant of the tire forcesis perpendicular to a line from the center of the tire to the vehiclecenter of gravity.

There are two main advantages in using these resultant forces to controlvehicle yaw (as opposed to purely tire lateral forces):

-   -   a. The resultant force can act at a greater lever arm,        increasing the maximum moment available.    -   b. Yaw rate can be controlled without requiring any steering.

If the forces are correctly controlled, the vehicle can be made torespond more quickly to a steering input and instability can be reduced.

To do this, the control of the wheel torques needs to consider:

-   -   a. Increasing torque on the one side must be balanced by a        reduction on the other side to avoid unnecessary acceleration.    -   b. Vertical load on each wheel—particularly as the vehicle        corners,    -   c. the vertical load on the inner wheels reduce and        drive/braking torque may cause wheel spin or wheel lock-up.    -   c. The addition of drive or braking torques at the rear may        result in loss of rear grip—leading to loss of control.    -   d. Any response must be safe and predictable.

Therefore, simply distributing the torque based on steering wheel anglewould achieve more yaw response (for the same steering input), but itmay not create any improvement in stability. It could even make thevehicle behavior less predictable.

One known approach is yaw rate feedback. For any steer angle and forwardvelocity, an ideal yaw rate can be calculated by assuming no tire slip,and using the wheel geometry to approximate the turn radius. Themeasured yaw rate is then used as feedback, giving a yaw error. Adifferential term (yaw acceleration) is included for damping. The outputis used to control the distribution of drive torque; i.e. for a leftturn, an additional torque is applied to the right, with an equalbraking torque applied to the left. These torques are in addition to the‘normal’ drive torque that maintains the vehicle forward velocity.

A limitation to conventional feedback control is that the system relieson measured yaw rate as an input signal. This measured response datawill also include ‘noise’ (high frequency waves created by road inputsand general vibration). In order to use the signal, the signal must befiltered. This unfortunately creates a time delay in the signal, and thefeedback becomes too late creating overshoot and oscillations in theresponse.

Electric Motor or Traction Drive Controls

Transmitting positive or negative values in Newton meters.

It is known that Direct Torque Control provides used in variablefrequency drives to control the torque (and thus finally the speed) ofthree-phase AC electric motors. This involves calculating an estimate ofthe motor's magnetic flux and torque based on the measured voltage andcurrent of the motor.

See patents by Depenbrock, takahashi and Noguchi direct self control anddirect torque control.

U.S. Pat. No. 4,678,248 discloses a method for controlling arotating-field machine supplied from an inverter, the output voltagesystem of the inverter being variable with respect to amplitude, phaseand frequency includes supplying amplitudes of stator flux componentsformed from measured stator current components and stator voltagecomponents as actual value of a flux control loop, and changing thephase and frequency of the inverter output voltage system with a fluxcontrol as a function of a predetermined stator flux reference value bydirectly setting-in the switching state of the inverter and an apparatusfor carrying out the method.

It is known that Vector motor control or field-oriented control providescontrol over three-phase AC electric motors by adjusting the outputcurrent of a VFD inverter in Voltage magnitude and Frequency. FOC is acontrol technique that is used in AC synchronous and induction motorapplications that was originally developed for high-performance motorapplications which can operate smoothly over the full speed range, cangenerate full torque at zero speed, and is capable of fast accelerationand deceleration but that is becoming increasingly attractive for lowerperformance applications as well due to FOC's motor size, cost and powerconsumption reduction superiority. Not only is FOC very common ininduction motor control applications due to its traditional superiorityin high-performance applications, but the expectation is that it willeventually nearly universally displace single-variable scalarvolts-per-Hertz (V/f) control.

What is needed is an improved apparatus and method to enable dynamicwheel control for energy and torque budgeting for each wheel.

BRIEF SUMMARY OF THE INVENTION

An apparatus for an electrically powered terrestrial vehicle applieselectrical energy to front wheels and to rear wheels. A control systemreceives desired acceleration inputs and provides target torquerequirements to a plurality of adaptive field-oriented motor controlcircuits. One or more three-phase alternating current synchronous motorsreceive voltage magnitude and voltage frequency to generate torque whichis applied through a reduction gear. The reduction gear may be coupledto one wheel or a pair of wheels. Forward acceleration is favored overdeceleration by a chosen ratio between reduction gearing of the frontaxle versus reduction gearing of the rear axle. An electrically poweredvehicle has diverse reduction gear ratios for front axle wheels and rearaxle wheels. Torque is budgeted to improve energy efficiency whenaccelerating in favor of the axle with greater reduction ratio. Torqueis budgeted to improve energy efficiency when cruising in favor of theaxle with lesser reduction ratio.

A system for deep autonomous vehicle control allocates positive andnegative torque to each wheel. A sensor system, navigation system, andcontrol system generally control speed and direction of a vehicle andthe an adaptive torque control system replaces conventional throttle andbraking systems improves performance and reduces reliance on thesteering system for skidding and slipping conditions due to dynamictraction and loading.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

To further clarify the above and other advantages and features of thepresent invention, a more particular description of the invention willbe rendered by reference to specific embodiments thereof which areillustrated in the appended drawings. It is appreciated that thesedrawings depict only typical embodiments of the invention and aretherefore not to be considered limiting of its scope. The invention willbe described and explained with additional specificity and detailthrough the use of the accompanying drawings in which:

FIG. 1 is a block diagram of a conventional processor used forperforming method steps in an apparatus;

FIG. 2 is a block diagram of an apparatus.

FIG. 3 is a flowchart of steps in a method performed by a processor; and

FIG. 4 is a schematic of a system embodiment.

DETAILED DISCLOSURE OF EMBODIMENTS OF THE INVENTION

Reference will now be made to the drawings to describe various aspectsof exemplary embodiments of the invention. It should be understood thatthe drawings are diagrammatic and schematic representations of suchexemplary embodiments and, accordingly, are not limiting of the scope ofthe present invention, nor are the drawings necessarily drawn to scale.

Referring now to FIG. 2, an embodiment of an apparatus for controllingvoltage magnitude and voltage frequencies at one or more AC motors. Aone wheel determination circuit 292 is coupled to a data bus 270. A twowheel determination circuit 294 is coupled to the data bus 270. A fourwheel determination circuit 296 is coupled to the data bus 270.Depending on the determination of the torque generation distributioncircuit 250, the addressable Adaptive Field-Oriented Control circuitsassociated with each AC motor will receive a digital indicia of voltagemagnitude and voltage frequency to be provided to their respectiveattached motors. The determination of the torque generation distributionis based on receiving a desired acceleration determination 210 from theoperator, and current speed determination 230 from sensors. The currentspeeds may include the wheel spin, the while slip, and otherenvironmental conditions.

Referring now to FIG. 3, one embodiment of the present invention is amethod performed by a computer processor when executing instructionsstored in non-transitory computer readable media, the method foroperating the vehicle control unit is described. At slowest speeds, onlyone wheel may need to be powered. When accelerating from low speed, thewheels with the maximum reduction gear may be optimally powered. When athreshold of speed has been attained, the wheels with lower reductiongear ratios may be optimally powered. Under certain conditions ofaggressive handling or poor conditions inferred from slip measurementsabove a threshold, all four wheels may receive separate voltage maximumand voltage frequency instructions. The method comprises the stepsreceiving desired acceleration indicia from the operator 310; receivingmeasurements of wheel slip and wheel spin from sensors 320; readingstored data values for reduction ratios of the front and rear wheels andthe maximum allow slip for retaining traction for the wheels 330;determining a positive or negative desired torque for each wheel 340;and transmitting a digital voltage maximum and voltage frequency 350 tothe respective control circuits.

Referring now to FIG. 4, a schematic is shown for an exemplary systemembodiment. A plurality of wheels are either front wheels 411 412 orrear wheels 417 418. Each wheel is coupled to a reduction gear whichhave a first reduction ratio 421 422 or a second reduction ratio 427428. Each reduction gear is powered by an AC motor 431 431 437 438. Themotors are provided with voltages at magnitudes and frequenciescontrolled by Adaptive Field-Oriented Control circuits 440 447 448. Theillustration shows that in one embodiment two wheels on one axle mayreceive the same torque or each wheel may receive a unique torque. Thevoltage magnitude and voltage frequencies for each wheel are determinedand distributed from a vehicle control unit 490.

One aspect of the invention is a 4 wheel power train for a terrestrialvehicle comprising: a plurality of electric motors; each electric motorcoupled directly to a wheel, each electric motor coupled to an AdaptiveTorque Control or an Adaptive Field-Oriented motor control circuit whichreceives a positive or negative torque command from a vehicle controlunit and provides the electric motor with voltage magnitude and voltagefrequency. Advantageously, a vehicle control unit budgets to torque totwo forward wheels, two rear wheels, or among all four wheels accordingto traction and desired acceleration.

In an embodiment the at least two electric motors are coupled to thefour wheels by at least two reduction gears, a first of two reductiongears having a first reduction ratio of first motor speed to first wheelspeed; a second of two reduction gears having a second reduction ratioof second motor speed to second wheel speed; and at least one variablefrequency drive control circuit coupled to the plurality of electricmotors.

In an embodiment, each of the front axle positioned wheels are coupledto one of a pair of reduction gears coupled to one of a pair of 3 phaseAC electric motors which when the terrestrial vehicle has beenaccelerated to a cruising speed receives current having voltagemagnitude and voltage frequency from the variable frequency drivecontrol circuit to overcome air drag and surface resistance.

In an embodiment the first reduction gears have a lower reduction ratiorelative to the second reduction gears and are coupled to the wheelspositioned on the front axle of the terrestrial vehicle.

In an embodiment, each of the rear axle positioned wheels are coupled toone of a pair of reduction gears coupled to one of a pair of 3 phase ACelectric motors which when the terrestrial vehicle is being acceleratedtoward a cruising speed receives voltage magnitude and voltage frequencyfrom the variable frequency drive control circuit to overcome inertia,air drag and surface resistance.

In an embodiment the second reduction gears have a higher reductionratio relative to the first reduction gears and are coupled to thewheels positioned on the rear axle of the terrestrial vehicle.

A method for optimizing electrical power consumption in a 4 wheel powertrain for a terrestrial vehicle by receiving acceleration, wheel spin,and wheel speed data from sensors and dynamically budgeting currentbetween motors coupled the rear wheels and motors coupled to the frontwheels according to the reduction ratio of the reduction gears when theterrestrial vehicle is being accelerated to a threshold.

A circuit budgets stored electrical power to front wheels and rearwheels of a vehicle according to reduction gear ratios and according tovehicle speed and acceleration.

Non-limiting illustrations of the subject matter include:

A system which includes: a plurality of wheels, each wheel being one ofa front wheel and a rear wheel; a plurality of reduction gears, eachreduction gear being one of a front reduction gear and a rear reductiongear; a plurality of alternating current electric motors (AC motors),each motor mechanically coupled to at least one wheel by at least onereduction gear; a plurality of adaptive field-oriented motor controlcircuits (AF-OC), each AF-OC electrically coupled to one or more ACmotors to provide voltage magnitude and voltage frequency andcommunicatively coupled to a vehicle control unit (VCU) to receivedigitally encoded signals which specify voltage magnitude and voltagefrequency; and the vehicle control unit to budget torque among allwheels, front wheels, or rear wheels according to indicia for desiredacceleration received from an operator.

In an embodiment, a pair of wheels are coupled to one reduction gearcoupled to one AC motor.

In an embodiment, each front wheel is coupled to one front reductiongear coupled to one AC motor, and each rear wheel is coupled to one rearreduction gear coupled to one AC motor.

In an embodiment, each AC motor is a 3-phase electric motor.

In an embodiment, a front reduction gear has a first reduction ratio anda rear reduction year has a second reduction ratio.

In an embodiment, the first reduction ratio is greater than the secondreduction ratio.

In an embodiment, the first reduction ratio is less than the secondreduction ratio.

In an embodiment, the apparatus further has sensors to measure wheelrotational speed (spin).

In an embodiment, the apparatus also has sensors to measure wheel sliprelative to a surface. That is, the distance the wheel travels isslightly more than or slightly less than its circumferance.

In an embodiment, the apparatus further has one or more generators orstores of direct current electricity coupled to each AF-OC.

Another aspect of the invention is a computer-implemented method foroptimizing energy efficiency and improving vehicle performance byexecuting instructions in a processor to: receive indicia for desiredacceleration from an operator; receive measurements of wheel slip andwheel spin; read stored values for each reduction ratio and maximumslip, determine positive or negative torque for each wheel; and,transmit digitally encoded voltage maximum and voltage frequency to eachAF-OC.

In an embodiment, more energy is provided to rear wheels whenaccelerating forward.

In an embodiment, more energy is provided to front wheels when notaccelerating forward.

In an embodiment, the voltage maximum and voltage frequency are limitedto enable no more than A % slippage when accelerating and—D % slippagewhen decelerating.

In an embodiment, all positive torque is provided to rear wheels whenforward acceleration is desired.

In an embodiment, all negative torque is provided to front wheels whenonly deceleration is desired.

In an embodiment, all positive torque is provided to front wheels whenonly air and road resistance needs to be overcome.

Another aspect of the invention is an apparatus for controlling anadaptive field-oriented electric motor which includes: a current speeddetermination circuit; a desired acceleration determination circuit; atorque generation distribution circuit; and a voltage magnitude andvoltage frequency determination circuit; whereby only front wheeladaptive field-oriented motor control circuits receive voltage magnitudeand voltage frequency torque generation signals when a threshold speedhas been attained and no further acceleration is desired, and wherebyonly rear wheel adaptive field oriented motor control circuits receivevoltage magnitude and voltage frequency torque generation signals whenacceleration is desired and a threshold speed has not been exceeded.

In an embodiment, the invention controls only one wheel at any forwardor reverse speed below a threshold.

In an embodiment, the invention controls all four wheels on thecondition of inclement weather, poor road quality, or aggressivecornering.

Applicant also discloses another aspect of the invention as an adaptivetorque control or field-oriented control (AF-OC) circuit to controlthree-phase AC motor output by providing current or voltage magnitudeand voltage frequency to single motor coupled to a wheel, eitherdirectly or in an embodiment through a reduction gear: the adaptivetorque control or AF-OC circuit comprising: DC power input circuits; ACpower output circuits; at least one microprocessor coupled tocomputer-readable non-transitory media; and data signal interfacecircuits, wherein the AF-OC circuit receives target torque commands,slip data, skid data, stability data, accelerometer data, and transmitsvia a network interface attainable torque; whereby adjustments toachieve target torque are provided by changes in current, voltagemagnitude, and frequency rather than throttle control for positivetorque and brake application for negative torque and whereby amendedtorque requests controlling current, voltage magnitude, and voltagefrequency outputs are controlled when slip data, skid data, or stabilitydata are received which cause the circuit to determine that a targettorque cannot be attained or sustained.

In an embodiment, the propulsion apparatuses each receive a desireddelta torque and control their own frequency, amplitude, phase, voltage,current, etc as needed.

In an embodiment a motor controller receives the delta torque values andsupplies the propulsion apparatuses with current or voltage at thenecessary phase, frequency, amplitude, or complex number.

In an embodiment, an adaptive torque control or AF-OC circuit iscommunicatively coupled to a plurality of other adaptive torque controlor AF-OC circuits and to a torque budgeter circuit, whereby targettorque commands are generated for each AF-OC circuit according tooperator controls in combination with attainable torque from each AF-OC,stability data, and accelerometer data.

In an embodiment, each adaptive torque control or AF-OC circuit adjustsits torque by control over current, voltage magnitude, and frequencymagnitude output when any other AFOC circuit determines a target torquecannot be attained or sustained, or transmits substantially large slipdata, skid data, or stability data.

In an embodiment, a rear wheel AF-OC circuit adjusts its voltagemagnitude and frequency magnitude output when a front wheel AFOC circuitdetermines a target torque cannot be attained or sustained, or transmitssubstantially large slip data, skid data, or stability data.

In an embodiment a torque budgeter circuit adjusts the target torque forrear wheel AF-OC circuits when at least one front wheel AFOC circuitdetermines a target torque cannot be attained or sustained, or transmitssubstantially large slip data, skid data, or stability data.

In a conventional system a central engine throttle and one or morehydraulic brake pistons is engage to modify vehicle yaw torque.Electrically controlled wheels offer more dynamic positive and negativetorque with far fewer mechanical linkages. Sensors locally attached toeach wheel can provide slip and skid information directly to an adaptivefield-oriented control (AF-OC) circuit. Each AF-OC circuit determineswhat its attainable torque can be for current conditions and transmitsit to a torque budgeting circuit. The torque budgeting circuit canreadjust its target torque commands in consideration of attainabletorque for each wheel, user operations (steering), and lateralacceleration and stability data.

In an embodiment, sensors locally attached to each electrically poweredwheel provide slip and skid information directly to an adaptive torquecontrol or adaptive field-oriented control (AF-OC) circuit. Eachadaptive torque control or AF-OC circuit determines what its attainabletorque can be for current conditions and transmits it to a torquebudgeting circuit. In an embodiment, the torque budgeting circuitreadjusts all target torque commands in consideration of attainabletorque for each wheel, user operations (steering), and lateralacceleration and stability data.

There are multiple ways to determine slip angle—some can use predictionbased on RPM data from the wheel, some can use external sensors for tiredeflection etc. In an embodiment a vehicle sensor measures land surfacevelocity and estimates RPM equivalents for each wheel. In an embodiment,the estimated RPM is compared by the torque control circuit with theactual RPM to determine when slip exceeds a maximum slip target.

One aspect of the invention is a method operable by a processorperforming steps encoded as instructions on a non-transitory media, tocontrol distribution of electric energy to at least one traction drivecoupled to a wheel comprising: sensing the steering direction and speedof the vehicle; on the condition of speed below a threshold,distributing power to one or more wheels associated with only one axleand if turning to only one wheel of the only one axle; on the conditionof speed above a threshold and when not turning, distributing power towheels associated with only one axle; on the condition of aggressivecornering applying yaw controlled power to budget torque among at leastfour wheels; on the condition of inclement weather applying yawcontrolled power to budget torque among at least four wheels; and on thecondition of poor road conditions applying yaw controlled power tobudget torque among at least four wheels.

The network communicates inputs such as measured yaw, vertical loadingof each wheel, measured torque, wheel orientation, wheel speed, and tireslip. In an embodiment, the network distributes these inputs to eachother wheel and to the yaw control apparatus.

The network communicates a desired torque value or a delta torque valuefor each traction drive and returns a confirmation or error message fromeach motor control circuit. Each traction drive may calculate parametersfor its own motor configuration.

Drive parameters include a current, voltage, frequency, or phase foreach wheel calculated by the yaw control apparatus. The drive parametersmay be transmitted to each wheel if the wheel's control circuit does notcalculate from the desired torque. In addition the network receives anddistributes a yaw prediction for future delta torques from a userinterface such as a gps or map or heads-up display or goggles.

A digital yaw control apparatus is communicatively coupled to a userinterface and to a network. The network connects at least one controldrive for each wheeled electric motor and provides a digital torquepacket to said control drive. The control drive provides current orvoltage to the wheeled motor. The control drive modulates the amplitudeof the current or voltage. The control drive modulates the frequency orphase of the current or voltage. The wheeled electric motor has a torquesensor and transmits the resulting torque back to the digital yawcontrol apparatus. An authentication circuit ensures that the correctwheeled motor receives the digital torque packet and that the packet wastransmitted by the correct control drive.

In an embodiment, a digital signal processor, or hardware discretecosine transform (DCT) or software algorithm can filter noise and highfrequency clutter from a feedback loop.

In one embodiment for two wheel control, the invention controls torqueat a left and at a right rear wheels or at a left and a right frontwheel, which eliminates the needs for at least one mechanicaldifferential gear or any electronically controlled differential.Depending on the steering angle, steering speed, throttle pedalposition, yaw velocity and vehicle speed, the apparatus applyingnegative torque to the left or right wheel, as required.

In one embodiment, this means that when entering a corner at high speed,moderate negative torque values are transmitted to the inside rearwheel. Simultaneously positive drive torque values transmitted to theoutside rear wheel supports the steering motion of the car.

One aspect of the invention is a system including a processor coupled tonon-transitory computer readable media and communicatively coupled to anoperator interface and communicatively coupled to one or more electricalpowered propulsion apparatuses.

The system determines a difference between desired vehicle yaw andmeasured vehicle yaw to determine a value for delta torque for eachpropulsion apparatus.

The system determines a value for positive or negative desired torquefor each of the one or more electrically powered propulsion apparatusesand transmits the desired target torque to each of the one or moreelectrically powered propulsion apparatuses.

In embodiments, the system transmits a value as a digital value; or inanother embodiment as an amplitude; or in another embodiment as a phaseangle or as a frequency. In embodiments the system determines andtransmits the value as a complex number. In an embodiment, the systemfurther has at least one yaw sensor. In an embodiment, the systemfurther has at least one pitch sensor. In an embodiment, the systemfurther has at least one roll sensor. In an embodiment, the systemfurther has at least one acceleration sensor.

In one embodiment of the invention, an electrically powered propulsionapparatus has one or more wheels, one or more electric motors, a motorcontroller and at least one sensor. The electrically powered propulsionapparatus further includes a surface sensor to report a vector of actualtravel direction and speed. In an embodiment the system also has an edgeof pavement sensor.

Applicant also discloses another aspect of the invention as a method tocontrol an apparatus by executing instructions and parameters whichcontrol dynamic vehicle responsiveness and reflect an operatorspersonality are accessible by an application programming interface(API). In an embodiment torque controlled electric motors may attachedto non-wheel traction mechanisms such as fans, propellers, airscrews,caterpiller drives, paddles, and powered legs.

DriveApps would be loaded either on the central computer (VCU) or aseparate user-provided computer that joins vehicle CANbus

DriveApp architecture allows multiple apps. Examples include:

1. Sports car

2. A tow trailer

3. AWD ATV 4. AWD SUV

5. multiple-motor water or ice/snow vessel6. multiple-motor aircraft7. dual powered wheelchair or personal transporter

API:

All API calls are performed via sending a controller area network (CAN)command into the traction CANbus. CAN ID defines recipient of thecommand—each inverter also called an Adaptive Field-Oriented Controller(AF-OC) circuit has a CAN ID, as does Vehicle Control Unit (VCU)apparatus and Battery Management System (BMS) circuit. All othersubsystems are controlled from within these modules (e.g., wheel #2 loadactuator is controlled from inverter #2 e.g. AF-OC-2, etc.)

1. Low-level (per-inverter)a. setTorque(wheel, torque, duration_ms)i. requests torque output of <torque> N*m from <wheel> wheel for<duration_ms> milli-secondsii. returns 0 on success, non-0 on error (error codes TBD)b. setSlipLevel(wheel, level)—sets level of aggressiveness of slipcontrol (low=street car use, high=race track)c. getTorque(wheel)—return torque value actually deliveredd. getLoad(wheel)—get wheel loading in Newtonse. getRPM(wheel)—get RPM of the wheelf. getSlipAngle(wheel)—get actual sleep angle

Method of operation includes at a field oriented motor controllercoupled to a network, receiving a set torque command which specifies awheel identifier, a value of target torque, and a duration whereintorque is in units of Newton*meters, and duration is in units ofmilliseconds; receiving a set slip level as an acceptable percentage ofrotation; determining a voltage magnitude and voltage frequency for amotor; providing 3 phase electric current at said voltage magnitude andvoltage frequency, receiving slip and skid measurements from theidentified wheel; and returning success or error codes, which includethe attainable torque at acceptable slip.

Mid-level (traction system—level)

Rate of change in vehicle position in 3-dimensional polar coordinates

getYawRate( )—get yaw rate in degrees/second from yaw sensor

i. getRollRate( )—get roll rate in degrees/second from roll sensorii. getAttitudeRate( )—get attitude rate in degrees/second from attitudesensor1. getAccel( )—get vehicle acceleration in mm/ŝ2(1 g=9,800 units)2. getLoad( )—get total vehicle weight (dynamic, can be different fromweight at rest due to aerodynamic lift etc)3. get[max/min][params]( )—get min and max values of the parameters fromthe per-inverter level. Example:

int getMaxSlipAngle( )

4. setAccel(accel)—request acceleration of the vehicle in mm/ŝ2 (can bepositive or negative)

A method for control of a vehicle by a processor performing the steps ofa process including transmitting commands and receiving measured orstored data. In an embodiment, each sensor responds when it isaddressed. In an embodiment, all sensors having the requested datarespond in order when no address is specified in the command. Inembodiments the commands and resulting data including at least one ofthe following: getYawRate—get yaw rate in degrees/second from yawsensor; getRollRate—get roll rate in degrees/second from roll sensor;getAttitudeRate—get attitude rate in degrees/second from attitudesensor; getAccel—get vehicle acceleration in mm/ŝ2(1 g=9,800 units);getLoad—get total vehicle weight (dynamic, can be different from weightat rest due to aerodynamic lift etc); and get[max/min][params]( )—getmin and max values of the parameters SlipAngle, Torque, SlipLevel, RPM,and Load.

In an embodiment, an operator control transmits to a vehicle controlunit a command to setAccel(accel)—request acceleration of the vehicle inmm/ŝ2 (can be positive or negative). In an embodiment, an autonomousvehicle control system is coupled by an API to the vehicle control unitto request acceleration and vectored torque.

High-level (car-level)

0. Battery Management System (BMS) functions

getMaxBattPower( )—get max battery power in kW. Used in VCU (VehicleControl Unit) to understand how much power is available to distributeinto wheels

i. getBattSOC( )—get state of charge of the battery in %ii. getBattAH( )—get remaining energy in the battery in AH (amp-hours)iii. getBattKWH( )—same in KWHrsiv. getBattV( )—get current battery voltage—used by VCU to predictmaximum possible power bandv. getBattIR( )—get current internal resistance of the battery—used byVCU to predict maximum possible power band

A method for operating a vehicle by a processor in a vehicle controlunit coupled by a network to a battery management system includestransmitting commands to read parameters including at least one of thefollowing: to get maximum battery power in kW: getMaxBattPower; to getstate of charge of the battery in percent: getBattSOC; to get remainingenergy in the battery in ampere-hours: getBattAH; to get remainingenergy in the battery in kilowatthours: getBattKWH: to get currentbattery voltage: getBattV; to get current measured internal resistanceof the battery: etBattIR.

Applicant also discloses another aspect of the invention as a system forpredictive torque budgeting which receives traction estimates forimpending road conditions. Traction measurements from previouslyrecorded measurements can be retrieved using global positioningcoordinates. Road geometry and incline is predicted from a stored 3Dmap. Traction measurements may be received from another vehicle in apeleton. Road conditions can be forecast from forward looking sensors onthe vehicle itself. Wheel slip and wheel skid measured by a front wheelis transmitted to the adaptive field-oriented motor control of thetandem rear wheel. Wheel loading sensors and actuators provide directfeedback on attainable torque.

In an embodiment, the system receives predicted yaw events from a map,gps system, user goggles or heads up display.

Intelligent traction prediction engine—data sources:

-   -   maps (curve ahead, etc) and GPS waypoints.    -   GPS waypoints and prior experience on same route    -   photo sensors before the front wheel to predict surface traction        (camera looking out 1 foot ahead will give us 10 ms time at 60        mph to modulate front wheel)    -   traction information from the front wheel fed into torque        commands to the rear wheels (that will see the same part of        pavement in ˜100 ms at 60 mph)    -   wheel loading sensors & actuators (to actively manage        instantaneous wheel loading)

Results: Based on the traction prediction method, the apparatus providestarget torque requests. The results include matching a rear wheel to itscorresponding front wheel; placing more energy on the rear axle wheelsand less on the front axle wheels for climbing, anticipating tightercornering and providing positive torque to a left side or providingnegative torque to a right side or vice versa or both. In some cases,negative torque is provided to one rear wheel while positive torque isprovided to the diagonally opposite wheel. The system anticipatesdesired yaw moments for the route and road conditions.

In an embodiment, a rear wheel AF-OC circuit adjusts its voltagemagnitude and frequency magnitude output when a front wheel AFOC circuitdetermines a target torque cannot be attained or sustained, or transmitssubstantially large slip data, skid data, or stability data.

In an embodiment a torque budgeter circuit adjusts the target torque forrear wheel AF-OC circuits when at least one front wheel AFOC circuitdetermines a target torque cannot be attained or sustained, or transmitssubstantially large slip data, skid data, or stability data.

Applicant also discloses another aspect of the invention as a method,which provides through an API, a process to adaptively control thrustinstead of throttle and brake operation. The vehicle control unitreceives acceleration requirements from the higher level autonomoussystems and determines positive or negative torque for each electricmotor driven wheel.

CONCLUSION

The claimed subject matter is easily distinguished from conventionalpower train differentials by electrically reallocating power from oneset of reduction gears to another set of reduction gears when theoperator calls for improved forward acceleration to overcome inertia.The effect is to dynamically exchange the performance characteristics ofthe vehicle among front wheel drive, rear wheel drive, and all wheeldrive.

The techniques described herein can be implemented in digital electroniccircuitry, or in computer hardware, firmware, software, or incombinations of them. The techniques can be implemented as a computerprogram product, i.e., a computer program tangibly embodied in aninformation carrier, e.g., in a machine-readable storage device or in apropagated signal, for execution by, or to control the operation of,data processing apparatus, e.g., a programmable processor, a computer,or multiple computers. A computer program can be written in any form ofprogramming language, including compiled or interpreted languages, andit can be deployed in any form, including as a stand-alone program or asa module, component, subroutine, or other unit suitable for use in acomputing environment. A computer program can be deployed to be executedon one computer or on multiple computers at one site or distributedacross multiple sites and interconnected by a communication network.

Method steps of the techniques described herein can be performed by oneor more programmable processors executing a computer program to performfunctions of the invention by operating on input data and generatingoutput. Method steps can also be performed by, and apparatus of theinvention can be implemented as, special purpose logic circuitry, e.g.,an FPGA (field programmable gate array) or an ASIC (application-specificintegrated circuit). Modules can refer to portions of the computerprogram and/or the processor/special circuitry that implements thatfunctionality.

FIG. 1 illustrates an exemplary programmable processor comprising a busor communication channel 111 coupling main memory 104, static memory106, mass storage memory 107, and a processor circuit 112 for executinginstructions, and in embodiments at least one interface to couple adisplay device 121, a selection command data input 123, and/or awireless interface 125.

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read-only memory ora random access memory or both. The essential elements of a computer area processor for executing instructions and one or more memory devicesfor storing instructions and data. Generally, a computer will alsoinclude, or be operatively coupled to receive data from or transfer datato, or both, one or more mass storage devices for storing data, e.g.,magnetic, magneto-optical disks, or optical disks. Computer-readablestorage media suitable for embodying computer program instructions anddata include all forms of non-volatile memory, including by way ofexample semiconductor memory devices, e.g., EPROM, EEPROM, and flashmemory devices; magnetic disks, e.g., internal hard disks or removabledisks; magneto-optical disks; and CD-ROM and DVD-ROM disks. Theprocessor and the memory can be supplemented by, or incorporated inspecial purpose logic circuitry.

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention. Forexample, other network topologies may be used. Accordingly, otherembodiments are within the scope of the following claims.

We claim:
 1. A system comprising: a plurality of wheels, each wheelbeing one of a front wheel and a rear wheel; a plurality of reductiongears, each reduction gear being one of a front reduction gear and arear reduction gear; a plurality of alternating current electric motors(AC motors), each motor mechanically coupled to at least one wheel by atleast one reduction gear; a plurality of adaptive field-oriented motorcontrol circuits (AF-OC), each AF-OC electrically coupled to one or moreAC motors to provide voltage magnitude and voltage frequency andcommunicatively coupled to a vehicle control unit (VCU) to receivedigitally encoded signals which specify voltage magnitude and voltagefrequency; and the vehicle control unit to budget torque among one ofall wheels, front wheels, and rear wheels according to indicia fordesired acceleration received from an operator.
 2. The system of claim 1wherein a pair of wheels are coupled to one reduction gear coupled toone AC motor.
 3. The system of claim 1 wherein each front wheel iscoupled to one front reduction gear coupled to one AC motor, and eachrear wheel is coupled to one rear reduction gear coupled to one ACmotor.
 4. The system of claim 1 wherein each AC motor is a 3-phaseelectric motor.
 5. The system of claim 1 wherein a front reduction gearhas a first reduction ratio and a rear reduction year has a secondreduction ratio.
 6. The system of claim 5 wherein the first reductionratio is greater than the second reduction ratio.
 7. The system of claim5 wherein the first reduction ratio is less than the second reductionratio.
 8. The system of claim 1 further comprising sensors to measurewheel rotational speed (spin).
 9. The system of claim 1 furthercomprising sensors to measure wheel slip relative to a surface.
 10. Thesystem of claim 1 further comprising one or more generators or stores ofdirect current electricity coupled to each AF-OC.
 11. A method foroptimizing energy efficiency and improving vehicle performance executinginstructions in a processor to receive indicia for desired accelerationfrom an operator; receive measurements of wheel slip and wheel spin;read stored values for each reduction ratio and maximum slip, determinepositive or negative torque for each wheel; and, transmit digitallyencoded voltage maximum and voltage frequency to each AF-OC.
 12. Themethod of claim 11 wherein more energy is provided to rear wheels whenaccelerating forward.
 13. The method of claim 11 wherein more energy isprovided to front wheels when not accelerating forward.
 14. The methodof claim 11 wherein the voltage maximum and voltage frequency arelimited to enable no more than A % slippage when accelerating and -D %slippage when decelerating.
 15. The method of claim 11 wherein allpositive torque is provided to rear wheels when forward acceleration isdesired.
 16. The method of claim 11 wherein all negative torque isprovided to front wheels when only deceleration is desired.
 17. Themethod of claim 11 wherein all positive torque is provided to frontwheels when only air and road resistance needs to be overcome.
 18. Anapparatus for controlling an adaptive field-oriented electric motorcomprising: a current speed determination circuit; a desiredacceleration determination circuit; a torque generation distributioncircuit; and a voltage magnitude and voltage frequency determinationcircuit; whereby only front wheel adaptive field-oriented motor controlcircuits receive voltage magnitude and voltage frequency torquegeneration signals when a threshold speed has been attained and nofurther acceleration is desired, and whereby only rear wheel adaptivefield oriented motor control circuits receive voltage magnitude andvoltage frequency torque generation signals when acceleration is desiredand a threshold speed has not been exceeded.
 19. The apparatus of claim18 which controls only one wheel at any forward or reverse speed below athreshold.
 20. The apparatus of claim 18 which controls all four wheelson the condition of inclement weather, poor road quality, or aggressivecornering.